go-ethereum event subscriptions doesn't work?

Question

I'm new to go-ethereum and even Golang in general so my terminology might be wrong, I'm guessing event handling is also referred to as "subscription"? Anyways, my actual issue is that I want to test out an event on a contract, but I can't seem to get any callbacks.

Here's my code:

func main() {
client, err := ethclient.Dial("wss://ropsten.infura.io/ws")


if err != nil{
    log.Fatal(err)
}


fmt.Println("We have a connection!")

privateKey, err := crypto.HexToECDSA("blablabla")
if(err != nil){
    log.Fatal(err)
}

publicKey := privateKey.Public()


publicECDSA := publicKey.(*ecdsa.PublicKey)

fromAddress := crypto.PubkeyToAddress(*publicECDSA)

nonce, err := client.PendingNonceAt(context.Background(), fromAddress)
gasPrice, err := client.SuggestGasPrice(context.Background())

auth := bind.NewKeyedTransactor(privateKey)
auth.Nonce = big.NewInt(int64(nonce))
auth.GasLimit = uint64(300000)
auth.GasPrice = gasPrice
auth.Value = big.NewInt(int64(0))

testAddr := common.HexToAddress("blablablabla")
testEvent, err := TestEvent.NewTestEvent(testAddr, client)
if(err != nil){
    log.Fatal(err)
}

resChan := make(chan *TestEvent.TestEventHandleEvent)

if(err != nil){
    log.Fatal(err)
}

start := uint64(0)
testEvent.WatchHandleEvent(&bind.WatchOpts{
    Context: context.Background(),
    Start: &start}, resChan)

if(err != nil){
    log.Fatal(err)
}

timer := time.NewTimer(5 * time.Second)
go func(){
    <- timer.C
    _, err := testEvent.Gotcha(auth)
    if(err != nil){
        log.Fatal(err)
    }
}()

code := <-resChan
fmt.Println(code)

close(resChan)

}

Here's my contract:

pragma solidity 0.4.25;

contract TestCon { event HandleEvent(uint64 code); address public owner;

constructor() public{
    owner = msg.sender;
}

function Gotcha() public payable {
    if(msg.sender == owner)
    {
        emit HandleEvent(10);  // I've deployed the contract from the same address. So this should match.
        return;
    }
    revert();
}

}

what am I doing wrong? Or is that a problem with my contract?

Answer 1

Here's a full working example of how to subscribe to event logs of a smart contract:

package main

import (
    "context"
    "fmt"
    "log"

    "github.com/ethereum/go-ethereum"
    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/core/types"
    "github.com/ethereum/go-ethereum/ethclient"
)

func main() {
    client, err := ethclient.Dial("wss://rinkeby.infura.io/ws")
    if err != nil {
        log.Fatal(err)
    }

    contractAddress := common.HexToAddress(" 0x147B8eb97fD247D06C4006D269c90C1908Fb5D54")
    query := ethereum.FilterQuery{
        Addresses: []common.Address{contractAddress},
    }

    logs := make(chan types.Log)
    sub, err := client.SubscribeFilterLogs(context.Background(), query, logs)
    if err != nil {
        log.Fatal(err)
    }

    for {
        select {
        case err := <-sub.Err():
            log.Fatal(err)
        case vLog := <-logs:
            fmt.Println(vLog) // pointer to event log
        }
    }
}

For more example check out the Ethereum Development with Go guide book.